Illumination devices are known, wherein a luminescent, or wavelength converting, material, such as a phosphor, is used for converting e.g. wavelength of light. One drawback with some luminescent materials is however their relative sensitivity to e.g. water or oxygen, which may cause a deterioration of the luminescent material.
In for example US 2011/0317397, this issue is addressed by providing a substantially transparent cover member which is hermetically sealed to the housing of the device, thereby enclosing quantum dots inside. The sealing operation can be done at a silicon wafer level, wherein the hermetical seal is formed by anodic bonding of a glass wafer onto a silicon wafer.
There is however still a need for an improved manufacturing method for obtaining an illumination device wherein the luminescent material is protected from exposure to the environment.